A little C program to dump contents of /proc/atags - count, size and md5 checksums

atags_print.c

#ifndef _DMADORE_MD5_H
#define _DMADORE_MD5_H

struct md5_ctx {
  /* The four chaining variables */
  unsigned long buf[4];
  /* Count number of message bits */
  unsigned long bits[2];
  /* Data being fed in */
  unsigned long in[16];
  /* Our position within the 512 bits (always between 0 and 63) */
  int b;
};

void MD5_transform (unsigned long buf[4], const unsigned long in[16]);
void MD5_start (struct md5_ctx *context);
void MD5_feed (struct md5_ctx *context, unsigned char inb);
void MD5_stop (struct md5_ctx *context, unsigned char digest[16]);

#endif /* not defined _DMADORE_MD5_H */

/* === The implementation === */

#define F1(x, y, z) (z ^ (x & (y ^ z)))
#define F2(x, y, z) F1(z, x, y)
#define F3(x, y, z) (x ^ y ^ z)
#define F4(x, y, z) (y ^ (x | ~z))

#define MD5STEP(f, w, x, y, z, data, s) \
    { w += f (x, y, z) + data;  w = w<<s | (w&0xffffffffUL)>>(32-s); \
      w += x; }

void
MD5_transform (unsigned long buf[4], const unsigned long in[16])
{
  register unsigned long a, b, c, d;

  a = buf[0];  b = buf[1];  c = buf[2];  d = buf[3];
  MD5STEP(F1, a, b, c, d, in[0] + 0xd76aa478UL, 7);
  MD5STEP(F1, d, a, b, c, in[1] + 0xe8c7b756UL, 12);
  MD5STEP(F1, c, d, a, b, in[2] + 0x242070dbUL, 17);
  MD5STEP(F1, b, c, d, a, in[3] + 0xc1bdceeeUL, 22);
  MD5STEP(F1, a, b, c, d, in[4] + 0xf57c0fafUL, 7);
  MD5STEP(F1, d, a, b, c, in[5] + 0x4787c62aUL, 12);
  MD5STEP(F1, c, d, a, b, in[6] + 0xa8304613UL, 17);
  MD5STEP(F1, b, c, d, a, in[7] + 0xfd469501UL, 22);
  MD5STEP(F1, a, b, c, d, in[8] + 0x698098d8UL, 7);
  MD5STEP(F1, d, a, b, c, in[9] + 0x8b44f7afUL, 12);
  MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1UL, 17);
  MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7beUL, 22);
  MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122UL, 7);
  MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193UL, 12);
  MD5STEP(F1, c, d, a, b, in[14] + 0xa679438eUL, 17);
  MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821UL, 22);
  MD5STEP(F2, a, b, c, d, in[1] + 0xf61e2562UL, 5);
  MD5STEP(F2, d, a, b, c, in[6] + 0xc040b340UL, 9);
  MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51UL, 14);
  MD5STEP(F2, b, c, d, a, in[0] + 0xe9b6c7aaUL, 20);
  MD5STEP(F2, a, b, c, d, in[5] + 0xd62f105dUL, 5);
  MD5STEP(F2, d, a, b, c, in[10] + 0x02441453UL, 9);
  MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681UL, 14);
  MD5STEP(F2, b, c, d, a, in[4] + 0xe7d3fbc8UL, 20);
  MD5STEP(F2, a, b, c, d, in[9] + 0x21e1cde6UL, 5);
  MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6UL, 9);
  MD5STEP(F2, c, d, a, b, in[3] + 0xf4d50d87UL, 14);
  MD5STEP(F2, b, c, d, a, in[8] + 0x455a14edUL, 20);
  MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905UL, 5);
  MD5STEP(F2, d, a, b, c, in[2] + 0xfcefa3f8UL, 9);
  MD5STEP(F2, c, d, a, b, in[7] + 0x676f02d9UL, 14);
  MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8aUL, 20);
  MD5STEP(F3, a, b, c, d, in[5] + 0xfffa3942UL, 4);
  MD5STEP(F3, d, a, b, c, in[8] + 0x8771f681UL, 11);
  MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122UL, 16);
  MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380cUL, 23);
  MD5STEP(F3, a, b, c, d, in[1] + 0xa4beea44UL, 4);
  MD5STEP(F3, d, a, b, c, in[4] + 0x4bdecfa9UL, 11);
  MD5STEP(F3, c, d, a, b, in[7] + 0xf6bb4b60UL, 16);
  MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70UL, 23);
  MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6UL, 4);
  MD5STEP(F3, d, a, b, c, in[0] + 0xeaa127faUL, 11);
  MD5STEP(F3, c, d, a, b, in[3] + 0xd4ef3085UL, 16);
  MD5STEP(F3, b, c, d, a, in[6] + 0x04881d05UL, 23);
  MD5STEP(F3, a, b, c, d, in[9] + 0xd9d4d039UL, 4);
  MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5UL, 11);
  MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8UL, 16);
  MD5STEP(F3, b, c, d, a, in[2] + 0xc4ac5665UL, 23);
  MD5STEP(F4, a, b, c, d, in[0] + 0xf4292244UL, 6);
  MD5STEP(F4, d, a, b, c, in[7] + 0x432aff97UL, 10);
  MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7UL, 15);
  MD5STEP(F4, b, c, d, a, in[5] + 0xfc93a039UL, 21);
  MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3UL, 6);
  MD5STEP(F4, d, a, b, c, in[3] + 0x8f0ccc92UL, 10);
  MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47dUL, 15);
  MD5STEP(F4, b, c, d, a, in[1] + 0x85845dd1UL, 21);
  MD5STEP(F4, a, b, c, d, in[8] + 0x6fa87e4fUL, 6);
  MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0UL, 10);
  MD5STEP(F4, c, d, a, b, in[6] + 0xa3014314UL, 15);
  MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1UL, 21);
  MD5STEP(F4, a, b, c, d, in[4] + 0xf7537e82UL, 6);
  MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235UL, 10);
  MD5STEP(F4, c, d, a, b, in[2] + 0x2ad7d2bbUL, 15);
  MD5STEP(F4, b, c, d, a, in[9] + 0xeb86d391UL, 21);
  buf[0] += a;  buf[1] += b;  buf[2] += c;  buf[3] += d;
}

#undef F1
#undef F2
#undef F3
#undef F4
#undef MD5STEP

void
MD5_start (struct md5_ctx *ctx)
{
  int i;

  ctx->buf[0] = 0x67452301UL;
  ctx->buf[1] = 0xefcdab89UL;
  ctx->buf[2] = 0x98badcfeUL;
  ctx->buf[3] = 0x10325476UL;
  ctx->bits[0] = 0;
  ctx->bits[1] = 0;
  for ( i=0 ; i<16 ; i++ )
    ctx->in[i] = 0;
  ctx->b = 0;
}

void
MD5_feed (struct md5_ctx *ctx, unsigned char inb)
{
  int i;
  unsigned long temp;

  ctx->in[ctx->b/4] |= ((unsigned long)inb) << ((ctx->b%4)*8);
  if ( ++ctx->b >= 64 )
    {
      MD5_transform (ctx->buf, ctx->in);
      ctx->b = 0;
      for ( i=0 ; i<16 ; i++ )
    ctx->in[i] = 0;
    }
  temp = ctx->bits[0];
  ctx->bits[0] += 8;
  if ( (temp&0xffffffffUL) > (ctx->bits[0]&0xffffffffUL) )
    ctx->bits[1]++;
}

void
MD5_stop (struct md5_ctx *ctx, unsigned char digest[32])
{
  int i;
  unsigned long bits[2];

  for ( i=0 ; i<2 ; i++ )
    bits[i] = ctx->bits[i];
  MD5_feed (ctx, 0x80);
  for ( ; ctx->b!=56 ; )
    MD5_feed (ctx, 0);
  for ( i=0 ; i<2 ; i++ )
    {
      MD5_feed (ctx, bits[i]&0xff);
      MD5_feed (ctx, (bits[i]>>8)&0xff);
      MD5_feed (ctx, (bits[i]>>16)&0xff);
      MD5_feed (ctx, (bits[i]>>24)&0xff);
    }

  /*for ( i=0 ; i<4 ; i++ )
    {
      digest[4*i] = ctx->buf[i]&0xff;
      digest[4*i+1] = (ctx->buf[i]>>8)&0xff;
      digest[4*i+2] = (ctx->buf[i]>>16)&0xff;
      digest[4*i+3] = (ctx->buf[i]>>24)&0xff;
    }*/

    static const char *hex = "0123456789abcdef";
    for ( i=0 ; i<4 ; i++ )
    {
      digest[4*i] = hex[(ctx->buf[i]&0xff) >> 4];
      digest[4*i+1] = hex[(ctx->buf[i]&0xff) & 0x0F];

      digest[4*i+2] = hex[((ctx->buf[i]>>8)&0xff) >> 4];
      digest[4*i+3] = hex[((ctx->buf[i]>>8)&0xff) & 0x0F];

      digest[4*i+4] = hex[((ctx->buf[i]>>16)&0xff) >> 4];
      digest[4*i+5] = hex[((ctx->buf[i]>>16)&0xff) & 0x0F];

      digest[4*i+6] = hex[((ctx->buf[i]>>24)&0xff) >> 4];
      digest[4*i+7] = hex[((ctx->buf[i]>>24)&0xff) & 0x0F];
    }
}

// ============================================================================

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

static const char *DEFAULT_PATH = "/proc/atags";

struct tag_header {
    uint32_t size;
    uint32_t tag;
};

struct tag {
    struct tag_header hdr;
    union {
        /* data structs */
    } u;
};

#define ATAG_NONE       0x00000000
#define tag_next(t)     ((struct tag *)((uint32_t *)(t) + (t)->hdr.size))

int main(int argc, const char **argv) {

    const char *path = DEFAULT_PATH;
    if(argc >= 2)
        path = argv[1];

    FILE *f = fopen(path, "r");
    if(!f)
    {
        fprintf(stderr, "Failed to open \"%s\"!\n", path);
        return -1;
    }

    char *data = NULL;
    char buff[128];
    size_t read = 0;
    size_t size = 0;

    while((read = fread(buff, 1, sizeof(buff), f)) > 0)
    {
        data = realloc(data, size+read);
        memcpy(data+size, buff, read);
        size += read;
    }

    struct tag *t = (struct tag*)data;
    size = 0;
    size_t count = 0;
    int i;
    struct md5_ctx context;
    unsigned char md5[33] = { 0 };

    for (; t->hdr.size; t = tag_next(t))
    {
        ++count;
        size += t->hdr.size*4;

        MD5_start (&context);
        for(i = sizeof(struct tag_header); i < (t->hdr.size*4); ++i)
            MD5_feed(&context, ((char*)t)[i]);
        MD5_stop (&context, md5);

        printf("Tag %02u: 0x%08X, size %06u, md5 %s\n", count, t->hdr.tag, t->hdr.size*4, md5);
    }
    printf("Total count: %u size: %u\n", count, size);

    free(data);
    fclose(f);
    return 0;
}